I put this unit in over the summer. Can't beat it for the price.

It sounds great, and has modern functionality like MP3/WMA disc support, AUX-IN jack, weather band, and a USB plug-in for memory stick MP3s.
I replaced a WRX 6-disc unit with this one, simply for the MP3 support... a single CD of MP3s replaces all those discs, and gives you unlimited mix capabilty, along with random play.
The fit is not *quite* perfect for the SS stereo surround, the unit is a hair bigger than the plastic trim, but if you play around with it a bit, it will click into place. Looks very nice, blends in with the stock interior, not flashy and it won't attract unwanted attention. Green background lighting, has a clock, easy-to-see and operate controls.
You do end up with a 1/2 DIN gap below the unit.... Installation is simple, just remove the two brackets off the original stereo, and screw them to the new one. The gap, well you can ignore it, blank it off, or find another bit of tech to fit into it; equalizer, boost controller, turbo timer, etc.
Two thumbs up!
I did have one issue with my unit; the power antenna trigger wire was dead, rather than send it back, I wired up a switch for the antenna to the switched power lead.
The place I got it from on Ebay also had the correct Subaru wire harness adapter...